More than 2.5 million people in the United States suffer from chronic venous insufficiency which includes disorders such as edema, stasis pigmentation, stasis dermatitis and stasis ulceration. Treatment of venous ulcers is difficult and costly, and their recurrence is frequent despite the treatment. Patients with venous ulcers may face partial or permanent disability and suffer the psychological and economic effects of losing mobility.
A promising approach to the treatment of chronic venous insufficiency is subfascial endoscopic perforator surgery (“SEPS”). Before discussing the SEPS procedure and the present invention's application to surgical procedures such as SEPS, it will be helpful to briefly review the venous anatomy of the leg and the pathophysiology of chronic venous insufficiency.
Venous blood is returned from the lower leg to the heart through a system comprising three types of veins: superficial veins which drain venous blood from tissue above the deep fascia in the lower leg, deep veins which drain blood from venous sinuisoids in the lower leg, and perforator veins which drain blood from the superficial veins into the deep veins.
Superficial veins include the greater saphenous vein, the lesser saphenous vein and the posterior arch vein. The lesser saphenous vein ascends from the lateral side of the foot and travels superiorly on the posterolateral side of the calf. The greater saphenous vein originates at the arch of the foot and eventually rises along the medial aspect of the lower leg. The posterior arch vein, or Leonardo's vein, drains blood from below the medial ankle, rises along the medial half of the leg and joins the greater saphenous vein.
The deep veins lie beneath the deep fascia and include the paired posterior tibial veins, the anterior tibial veins, the peroneal veins and the popliteal vein. Some of the deep veins originate at the foot and ascend the lower leg.
The perforator veins which connect the superficial veins to the deep veins are called “perforator” veins because they penetrate the deep fascia as they travel from the superficial veins to the deep veins. Perforator veins include anterior perforator veins situated on the anterolateral surface of the lower leg, lateral perforator veins found on the posterolateral surface of the lower leg, and medial perforator veins located on the medial side of the lower leg. The medial perforator veins further include the Cockett perforator veins which are located toward the ankle.
The blood pressure in veins is much lower than the blood pressure in arteries, often by a factor of fifty. The low venous blood pressure itself is incapable of returning venous blood, particularly in the lower limbs, to the heart. As a result, skeletal muscles in the lower limbs assist by contracting to pump venous blood from the lower limbs to the heart. For example, the veins in the calf muscle are surrounded by a tight muscle-fascial envelope which forms a “calf-muscle pump”. Contraction of the calf muscles compresses the veins and propels the venous blood upward to the heart.
When the calf muscles are relaxed (diastolic phase), the valves of the perforator veins are open which permits blood to flow one-way from the superficial veins to the dilated soleal sinusoids of the deep vein system. The next muscle contraction (systolic phase) expels the blood temporarily stored in the soleal sinuisoids into the popliteal and femoral veins of the deep vein system. During the systolic phase of the calf-muscle pump, the valves of the perforator veins are closed to prevent blood from being expelled back through the perforator veins and into the superficial veins. The valves of the perforating veins further protect various subcutaneous tissues from the muscular systolic pressure generated by the calf-muscle pump, which pressure may range from 150 to 300 mm Hg.
When the valves in the perforator veins fail to function correctly (perforator vein incompetence), blood will flow backward (reflux) from the deep veins to the superficial veins, thereby failing to return to the heart. Perforator vein incompetence may be caused, for example, by local trauma, long-term saphenous incompetence, or minor calf-vein thrombosis.
Reflux of blood due to perforator vein incompetence may result in chronic ambulatory venous hypertension, that is, a persistent case of elevated ambulatory venous pressure. Patients with chronic ambulatory venous hypertension may have symptoms such as aching, fullness, or tiredness in their lower leg. Chronic ambulatory venous hypertension may further lead to venous ulceration, a painful and often debilitating condition. In fact, the more extensive and the more distal the reflux, the greater the chance that the patient will develop a venous ulcer.
According to one study, 80–90% of incompetent perforator vein cases involve the medial perforator veins in the lower leg, 15% involve the lateral perforator veins, and 5% involve the anterior perforator veins. Of the 80–90% of incompetent perforator vein cases which involve the medial perforator veins in the lower leg, most occur near the region of Cockett's perforator veins. Cockett's perforator veins are located at roughly six, twelve and eighteen centimeters from the heel sole.
Treatment of chronic venous insufficiency includes noninvasive treatments such as leg elevation to foster draining the blood out of the lower leg, compression by application of bandages to reduce venous pressure in the lower leg, and topical therapies to promote healing of ulcerous wounds. Treatment also may include invasive treatments such as sclerotherapy, skin grafting, stripping of superficial veins, open subfascial perforator surgery, subfascial endoscopic perforator surgery and deep vein reconstruction. The proper treatment or treatments to apply depend on the particular circumstances of the patient's venous dysfunction. Skin grafting may be used to accelerate healing of ulcerous wounds through the covering of wounds with split-skin, mesh, or pinch grafts. Skin grafting, however, does not eliminate the underlying cause of venous dysfunction. Instead, it treats the symptoms of venous dysfunction such as the ulcer. Thus, recurrence of ulcers is likely. Sclerotherapy involves injecting a sclerosing solution into, dysfunctional blood vessels to cause them to obliterate. The removal of dysfunctional vessels reduces venous reflux. Similarly, superficial vein stripping involves excising dysfunctional superficial veins by subcutaneous dissection in order to reduce venous reflux. However, the removal of superficial veins does not resolve reflux problems in the perforator veins. Deep vein reconstruction is reserved for patients whose ulcers have failed to respond to all other kinds of therapy. Deep venous reconstruction includes direct valve repair (valvuloplasty), valve transposition and valve transplantation.
Open subfascial perforator surgery involves making at least one long incision in the lower leg to gain access to the perforator veins which are then ligated or removed. When incompetent perforator veins are removed, new perforator veins begin to grow through a regeneration process. As a result, dysfunctional perforator veins are replaced by regenerated perforator veins. Open subfascial perforator surgery tends to prevent recurrent venous ulceration because this treatment attacks a root cause of perforator venous dysfunction.
However, incisions near or at the locations of diseased skin (e.g., ulcers) may result in wound complications and delayed wound healing. Thus, there is a need for a surgical procedure which uses an incision site more distant from the area of ulcerative damage and yet provides access to the underlying perforator veins.
While subfascial endoscopic perforator surgery (SEPS) is not indicated for all venous dysfunctions or for all patients, it permits surgeons to make an incision more remote from an ulcerous wound and yet gain access to perforator veins underlying the ulcer. SEPS approaches vary. Some surgeons use a one-port approach where the scope and working instruments are introduced through a single incision in the proximal calf. In the dual port approach which enhances visualization, one port is used for the scope and the other port is used for the working instruments. The space created by either the single or dual port approach may be optionally insufflated with gas, such as CO2, or any other suitable fluid. The SEPS approach requires the dissection of the subfascial plane so that surgical instruments can access and ligate the dysfunctional perforator veins. Dissection of the subfascial plane may be accomplished manually with surgical instruments. Besides blunt dissection, dissection can also be performed by inserting a deflated balloon to the subfascial tissue plane and then inflating the balloon to cause dissection of tissue layers along the tissue plane. A traumatic balloon dissection of the subfascial plane exposes the perforator veins and creates space for the surgeon to access and ligate dysfunctional perforator veins, while minimizing trauma to the blood vessels, long-standing ulcers and damaged tissues. Compared to blunt dissection, balloon dissection results in less bleeding, due in part to the atraumatic nature of tissue dissection and in part to the tamponade effect of the balloon on surrounding tissues. Thus, the balloon offers the advantage of minimizing trauma to certain tissues (e.g., veins) while accomplishing sufficient dissection of tissues to afford visualization, if desired, as well as access to the vein.
The Spacemaker SEPS balloon device (model number VDB 300), which is manufactured and sold by General Surgical Innovations, Inc., the assignee of the present patent application, is a balloon device which may be used to dissect the subfascial plane for a SEPS procedure. This balloon is mounted to a cannula and inflates to a predictable cylindrical shape. The diameter of the cylindrical balloon is generally uniform along the length of the balloon.
Because many of the incompetent perforator veins occur near the ankle where blood is the furthest from the heart, resulting tissue damage and venous ulcers may occur near the ankle. Thus, there is a need for an improved balloon dissection device which further minimizes trauma to the already deteriorated tissue and which permits further dissection of the subfascial space at a location close to the ankle.